> Is it normal ?

It is - if you zoom in closely along the bottom edge you should be able to see that those pieces are all connected. The connection is a quite skinny piece so it is somewhat difficult to see unless you zoom in a lot.

It looks like Hexagon has done a proper job of handling the complex ngons.

The quality on ngon handling varies quite a lot because when it comes time to render the ngon, it must be triangulated. It is not a particularly easy task to create a triangulator that works properly on complex outlines.

- Michael